1. Field of the Invention
The invention relates to a sample-collecting system for gaseous or vaporous condensable radioactive substances contained in the ambient air, especially for collecting traces of tritium via the T.sub.2 O vapor content contained in the exhaust air of a nuclear installation or a nuclear power generating station.
2. Description of the Prior Art
According to the safety rules of the Nuclear Engineering Committee (KTA), part 1: Measurement and Monitoring of the discharge of radioactive substance in the flue exhaust gas during the intended operation, it is stated (KTA 1503.1, version of February, 1979) with regard to tritium monitoring that tritium samples are to be taken continuously from the flue exhaust air and to be evaluated quarterly, and specifically in light-water and high-temperature reactors.
Tritium is the heaviest hydrogen isotope. Its atomic weight is 3.01686 (referred to .sup.12 C); it is radioactive. In nuclear installations and, in particular, in nuclear power plants, traces of tritium are discharged into the environment with the exhaust air. Conclusions as to the operating state of the reactor can be drawn from the amount of tritium traces. In nuclear installations and, in particular nuclear power stations, the tritium traces contained in the exhaust air must be monitored, as mentioned, reliably over extended periods of time and the collected samples must then be subjected to laboratory tests. This is generally not done at the site where the sample is taken, but in a laboratory remote therefrom. A particular problem involved in such a sample-collecting device is that as few as possible or no manual operations are to be performed during the sample-taking interval in the device. The operation of the sample-collecting device should be intrinsically safe as far as possible, requiring only that the collected sample be removed at the end of the sample taking interval and exchanged for an empty exchanged vessel. Such a continuous sample taking operation puts more stringent requirements on the pneumatic-hydraulic as well as on the electrical system of the sample collecting device.